President Donald Trump called Chinese leader Xi Jinping a master poker player, suggesting that China may be playing North Korea and the United States off each other in a lead up to the historic summit scheduled to take place between the two countries on June 12.

Speaking to reporters during a joint press conference in the Oval Office with South Korean President Moon Jae-in, Trump said that North Korean leader Kim Jong Un had become less willing to negotiate after visiting China on a surprise trip in early May. The North Korean leader met with Xi twice during a 40 day period.

“I think there was a change in attitude from Kim Jong Un after his meeting with Xi. There was a difference after Kim Jong Un left China the second time. President Xi is a world class poker player. Maybe nothing happened, I'm not blaming anybody. But there was a different attitude from the North Korean folks after that second meeting,” Trump said during the press conference, after stressing that he has a good personal relationship with President Xi.

Moon was visiting Washington on Tuesday to urge President Trump to continue with the North Korea meeting; Trump and North Korean leader Kim Jong Un had been scheduled to meet in Singapore next month. But over the past week, leaders from both countries have suggested that the meetings could be canceled or stalled. In a statement released last week, North Korea threatened to pull out of the talks altogether. During his meeting with Moon, Trump said that it’s possible the meeting, which would focus on North Korea's nuclear program, will be canceled or postponed.

"We're moving along. We'll see what happens. There are certain conditions we want to happen. I think we'll get those conditions. And if we don't, we won't have the meeting," Trump said about the summit. "Frankly, it has the chance to be a great, great meeting for North Korea and a great meeting for the world. If it doesn't happen, maybe it will happen later. Maybe it will happen at a different time. We will see. We are talking."

Trump has stressed that China has a role to play. During the Oval Office meeting Tuesday and in a Tweet on Monday, Trump urged China to close its border with North Korea to cut off trade to the country and apply further diplomatic pressure in the lead up to the meeting. Trump may not, however, have much leverage with China, as his administration is currently entering into a trade war with the country.